1. Field of the Invention
The present invention relates to pistons, to precursors for making containers, to containers, to product-containing containers, to methods of making such pistons, precursors, containers and product-containing containers, to methods of dispensing, and to methods of filling containers. In another aspect, the present invention relates to pistons for pressure operated dispensing containers, to pressure operated dispensing containers utilizing a piston longitudinally slidable within the container, product-containing containers, to methods of dispensing, and to methods of filling. In even another aspect, the present invention relates to pistons for pressure operated dispensing containers, to pressure operated dispensing containers utilizing a piston longitudinally slidable within the container, product-containing containers, to methods of dispensing, and to methods of filling, all of which provide improved resistance to “leak through” of product past the piston.
2. Description of the Related Art
Pressure operated dispensing containers which utilize a piston longitudinally slidable within the container are well known in the art. These types of containers are used to dispense any number of products, for example many consumer products such as shaving gels.
Such a pressurized container is generally cylindrically shaped, and includes a movable piston disposed therein, which divides the container reservoir into two chambers, i.e., the chamber above the piston or the “upper chamber” wherein the product composition resides, and the chamber below the piston or the “lower chamber” wherein the compressed fluid is injected or pressure filled. Said compressed fluid is at a pressure higher than ambient and higher than that of the product in the upper chamber. A dispensing valve is positioned to be in liquid communication with the product containing composition compartment, to allow for dispensing of the product composition for use.
The piston is roughly in the form of an inverted cup, with a curved surface designed to closely match the inside-top of the container such that in its penultimate position at the top of the container, the piston will have forced and dispensed essentially all of the product composition in the upper chamber through the dispensing valve. This helps in minimizing product composition left unused or undeliverable inside the container. In addition, the piston has an upper and an annular skirt or sidewall which extends down from the upper surface. The upper surface acts as a barrier to separate the product from the gas. The annular sidewall of the piston stabilizes and positions the piston in the container and provides a surface which rides on the inner wall of the container.
While the exact details of loading may vary from industry-to-industry and product-by-product, the following is a general description. The product to be dispensed is loaded into the upper chamber of the container under pressure. The loading is a three stage operation, with each stage occurring at a different index position on the loading machine. During the first stage, known as the fill stage the product is introduced into the can above the top of the piston. During the second stage, known as the pressure stage a pressure differential is created above and below the piston to force some of the product down around the periphery of the piston between the piston sidewall and the container. During the third stage, known as the pushup stage, the piston is pushed toward the top of the container. This pushup stage also causes product to seep down around the periphery of the piston. After the loading of the product into the upper chamber is completed, propellant is loaded into the lower chamber under pressure. In use, when the valve at the top of the container is opened, the propellant pushes the piston toward the top of the container through the valve.
In operation of, for example, a pressurized container of shaving gel, a user will activate the product dispensing valve, whereupon the pressurized gas The wall supports are arranged in vertically aligned pairs and extend along the disk substantially one-half the radius thereof. The cylinder has upper and lower wiping edges defined by the concave wall and the entire piston assembly may be integrally molded from a synthetic plastic material.
U.S. Pat. No. 3,901,416, issued Aug. 26, 1975, to Robert S. Schultz, discloses a piston-operated pressurized container adapted for top-loading with viscous foods or other viscous products, the body of the piston having a substantially smaller diameter than the diameter of the container. The outer periphery of the piston is provided with a resilient flange member that maintains a light sealing pressure on the interior surfaces of the container, allowing the piston to move upwardly within the container. The inventive method provides enhanced assurance against product leakage and against propellant-contamination of product, prior to selective product discharge as desired.
U.S. Pat. No. 3,987,941, issued Oct. 26, 1976, to Alfred V. Blessing, discloses a container for cooked liquid food substances in which there is provided a follower lid or upper cover capable of following the level of the liquid as the food substance is removed from the container. The invention includes a particular construction of lid and seal that allows for free upward and downward movement of the lid in contact with the liquid as the liquid level changes. In this manner, the liquid is not in contact with air which would cause its contamination and loss of flavor.
U.S. Pat. No. 4,023,717, issued May 17, 1977, to Schultz, discloses a pressurized container for viscous foods or other viscous products in which the body of the piston includes an axially intermediate flexible circumferential band which lightly contacts or is expandable in the presence of loading pressure exerted by propellant gas. The band thus develops light sealing contact with the interior wall surface of the container, and such contact effectively isolates unexpelled product from the gas-pressure side of the piston, regardless of the extent to which product has been expelled.
U.S. Pat. No. 4,106,674, issued Aug. 15, 1978 to Schultz, discloses a pressurized container for viscous foods or other viscous products in which the body of the piston includes, adjacent to the head end, a flexible circumferential band which lightly contacts or is expandable in the presence of loading pressure exerted by propellant gas. The band thus develops light sealing contact with the interior wall surface of the container, and such contact effectively isolates unexpelled product from the gas-pressure side of the piston, regardless of the extent to which product has been expelled. The piston further includes a circumferentially continuous tail structure which is connected to and axially spaced from the expandable band and which serves to stabilize the piston against malfunction in the course of its single product-expelling stroke.
U.S. Pat. No. 4,234,108, issued Nov. 18, 1980, to Diamond, discloses a piston for an aerosol container, particularly adapted for insertion through the top of the container. The piston includes an annular, cylindrical collar near its top end and a conical outwardly flaring flange atop the cylindrical collar, with the flange flaring wider toward the top of the container, whereby the flange scrapes the container interior as it moves up. The cylindrical collar is more flexible than the conical flange to ease insertion of the piston and for more effective piston sealing despite the piston cocking in the container. An anti-cocking ring is provided on the piston.
U.S. Pat. No. 4,323,177, issued Apr. 6, 1982 to Nielsen, discloses an ejection piston for use in cylindrical dispensing containers or packages of the type containing viscous or plastic masses such as sealing compounds and adhesives. The piston assembly comprises a piston part having a peripheral skirt as well as an arched piston top, and a separate piston actuating member arched in a direction opposite to the piston top. An ejection pressure is applied to the actuating member and transmitted to the piston top whereby the effective diameter of the piston top is slightly increased. An annular sealing sleeve for receiving the piston skirt and the adjacent free end of the cylindrical container during storage may be formed integrally with the piston actuating member.
U.S. Pat. No. 4,703,875, issued Nov. 3, 1987 to Malek, discloses an injection-molded piston for an aerosol container with a face portion for contacting and exerting pressure on material to be dispensed, and a thin, flexible skirt depending axially from and circumscribing the face portion for forming an effective seal against the inside wall of the container. The outer wall of the skirt is continuous, while the circumference of the inner wall has alternating areas of constant thickness along said areas and areas of minimum thickness, the curved portions forming with the outer wall a plurality of sections, the thickness and circumferential extent of each of which decrease axially along the skirt toward its distal end. The piston includes a depending extension on the skirt which aids sealing.
U.S. Pat. No. 4,913,323, issued Apr. 3, 1990, to Scheindel, discloses a piston that is longitudinally slidable within a pressurized container to dispense materials from the container. The piston has a generally annular sidewall and a traverse barrier wall at one end of the sidewall and integral therewith to define a cup-shaped closure open at one end. An annular step is provided on the sidewall which divides the sidewall into two segments, an upper segment and a lower segment. The annular step is below and spaced from the barrier wall. The upper segment has a diameter smaller than the diameter of the lower segment and the clearance between the upper segment and the interior of the container is substantially greater than the clearance between the lower segment and the interior of the container.
U.S. Pat. No. 5,127,556, issued Jul. 7, 1992, to Sporri, discloses an aerosol can piston and container system, employing an aerosol can with a sidewall which is necked in at the bottom and a low mass piston with recessed, depending legs. The piston has a lower skirt portion, the outermost diameter of which is slightly smaller than the diameter of the inner wall of the can above the necked-in portion. The legs depending from the piston have an effective outer diameter somewhat less than the inside diameter of the lower necked-in portion of the can sidewall and depend sufficiently downward to sit on the can bottom countersink while maintaining the skirt of the piston at a level just above the level at which the can sidewall necks inwardly. The legs thus stabilize the piston and prevent tipping and canting. In an alternative embodiment the piston also includes a plurality of vertical columns protruding from its sidewall to further stabilize the piston.
However, in spite of the above advancements, there still exists a need in the art for pistons, for container precursors, for containers, for product-containing containers, for methods of dispensing, for methods of filling containers, and for methods of making such pistons, container precursors, and containers.
There exists another need in the art for pistons, for container precursors, for containers, for product-containing containers, for methods of dispensing, for methods of filling containers, and for methods of making such pistons, container precursors, and containers, which reduce the “leak through” problem as compared to the prior art.
There exists even another need in the art for pistons, for containers, for container precursors, for product-containing containers, for methods of dispensing, and for methods of filling containers, and for methods of making such pistons, container precursors, and containers, which do not suffer from the disadvantages of the prior art apparatus and methods.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.